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Atomic Force Microscopy - Patent 5144833


The present invention relates to atomic force microscopy and specifically to an atomic force microscope which employs a micromachined cantilever beam in order to achieve atomic resolution. In addition, the atomic force microscope is capable ofoperation in vacuum, air or liquid environments, of scanning a large surface area and of providing common mode rejection for improved operation.Atomic force microscopy is based upon the principle of sensing the forces between a sharp stylus or tip and the surface to be investigated. The interatomic forces induce the displacement of the stylus mounted on the end of a cantilever beam. Inits original implementation, a tunneling junction was used to detect the motion of the stylus attached to an electrically conductive cantilever beam. Subsequently, optical interferometry was used to detect cantilever beam deflection.As described by G. Binnig et al, in Phys. Rev. Lett., vol. 56, No. 9, March 1986, pp. 930-933, a sharply pointed tip is attached to a spring-like cantilever beam to scan the profile of a surface to be investigated. The attractive or repulsiveforces occurring between the atoms at the apex of the tip and those of the surface result in tiny deflections of the cantilever beam. The deflection is measured by means of a tunneling microscope. That is, an electrically conductive tunnel tip isdisposed within the tunnel distance from the back of the cantilever beam, and the variations of the tunneling current are indicative of the beam deflection. The forces occurring between the tip and the surface under investigation are determined from themeasured beam deflection and the characteristics of the cantilever beam.In articles by G. McClelland et al, entitled "Atomic Force Microscopy: General Principles and a New Implementation", Rev. Progr. Quart. Non-destr. Eval., vol. 6, 1987, p. 1307 and Y. Martin et al, entitled "Atomic force microscope-forcemapping and profiling on a sub 100- .ANG. scale", J. Appl. Phys., vol. 6

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